When the original Portal launched alongside The Orange Box in 2007, there were plenty of fans and critics who thought it was perfect. Players loved that the game offered something completely new, and the game's self-contained story came with a definitive sense of closure -- audiences were completely satisfied with what they got. With such a hard act to follow, why, then, did Valve set out to create Portal 2?

According to Valve writers Chet Faliszek and Erik Wolpaw, the sequel came about for one reason: The team at Valve just wanted to work on another Portal game.

"The bottom line was Portal 1 was made by a team of students that we picked up from DigiPen who had made a small demo game called Narbacular Drop. So that left like 150 people at Valve who didn't get to work on Portal, but who loved Portal. After we shipped The Orange Box, that left a bunch of people wanted to work on a Portal game," Wolpaw said during a presentation at GDC 2012.

As Wolpaw and Faliszek explain in the above GDC Vault video of their talk, Valve then set out to defy expectations and top the game that many said couldn't be topped. At the outset, the team knew it had to surprise audiences all over again, and in order to do so the studio needed to distance itself from the original game by leaving certain concepts on the cutting room floor.

When drafting up concepts for Portal 2, Valve chose to keep Aperture Science as the central environment for the game, but chose to abandon major elements like Chell, GlaDOS...and even portals.

"Yeah, sure, the name was in the title, but we figured we'd worry about the later," Faliszek joked.

Of course, the final version of Portal 2 ended up very unlike that initial concept, and to see how the game made that eventual transition, check out Faliszek and Wolpaw's presentation above. Simply click the Play button to start the video.

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